Shell中的算数运算

echo $((a+b))
expr $a + $b
let "a=1+2";echo $a
a=5;let "a+=10";echo $a
echo "1+2" | bc -l -q

echo $((a-b))
let "a=1-2";echo $a
a=19;let "a-=50";echo $a
expr $a - $b
echo "3-2" | bc -l -q

echo $((a*b))
expr $a \* $b
let "num=2*3";echo $num
echo "3*3" | bc -l -q

echo $((a/b))
expr $a / $b
echo "3/3" | bc -l -q

echo $((3**4))
let "num=3**4"; echo $num

echo $((4%3))
echo "4%3" | bc -l -q

echo "scale=100; 4*a(1)" | bc -l -q